I think the answer is A. I know it's Planet X.
Explanation:
When Henri Becquerel investigated the newly discovered X-rays in 1896, it led to studies of how uranium salts are affected by light. By accident, he discovered that uranium salts spontaneously emit a penetrating radiation that can be registered on a photographic plate.
Density = mass / volume
D = 1 x 10⁴ / 2
D = 5000 kg/m³ in g/cm³:
1 kg/m³ ---------------- 0.001 g/cm³
5000 kg/m³ ----------- ??
5000 x 0.001 / 1 => 5.0 g/cm³
hope this helps!
D.
Gastropods live in every conceivable habitat